This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Creation of a successful HIV vaccine will require development of an immunogen that will generate cellular immunity with sufficient cross-clade breadth to deal with the extreme genetic diversity of the virus. Recently it has been suggested that vaccines based on centralized HIV gene sequences might provide a solution to the problem posed by the genetic heterogeneity of the circulating strains of HIV. Both consensus and polyvalent mosaic immunogens are based on centralized gene sequences. The present study was designed to explore the breadth of CD4+ and CD8+ T lymphocyte responses generated by vaccination with polyvalent mosaic as compared to vaccination with consensus immunogens.